Many vehicular wheel drive assemblies for tractors, lift trucks and the like employ planetary gear sets individually having an input sun gear, an output planet carrier, and a stationary ring gear. The planetary gear set provides the required speed reduction and corresponding torque increase between the differential and the wheel. Also, oil-cooled disc packs have been incorporated in the planetary wheel drive assemblies to provide the desired braking capacity. Such assemblies are shown, for example, by the following U.S. Patent Nos.: 3,115,204 issued Dec. 24, 1963 to D. S. Dence; 3,157,239 issued Nov. 17, 1964 to R. J. Bernotas; 3,301,359 issued Jan. 31, 1967 to C. R. Cole et al; 3,754,625 issued Aug. 28, 1973 to J. W. Voth et al; 4,010,830 issued Mar. 8, 1977 to A. T. logus et al; 4,037,694 issued July 26, 1977 to B. W. Keese; 4,142,615 issued Mar. 6, 1979 to P. Sidles, Jr. et al; and 4,317,498 issued Mar. 2, 1982 to N. F. Jirousek et al.
For the most part these wheel drive assemblies have proven to be very satisfactory. However, when they are downsized for vehicles where space is at a premium, such as for a lift truck, the serviceability of the components becomes adversely affected. Specifically, the overall width of the lift truck is selected so that it can maneuver in the narrow aisles of a factory or warehouse. Since the transverse width is limited, the space available for the planetary gear set, the wet disc brake mechanism and the supporting bearing assemblies also is limited.
As a result of such limitations in transverse width, there is the problem of where to put the disc brake mechanism relative to the planetary gear set in order to allow individualized and independent servicing thereof. Moreover, if the disc brake mechanism is positioned inside the stationary hollow spindle then the two opposed bearing assemblies that are mounted on the spindle and that support the wheel structure must be increased in diameter at substantial expense. Then too, it is desirable to locate these bearing assemblies at a maximum axially spaced condition conducive to better supporting the wheel structure, and with the mid-plane of the wheel or wheels mounted thereon being located generally centrally between the bearing assemblies for maximum balance.
Accordingly, what is needed is a sturdy and structurally compact planetary wheel drive assembly that incorporates a planetary gear set and a disc brake mechanism in locations that minimize the overall cost thereof, while allowing independent servicing and/or subassembly of these components with minimal effort and affect on the vehicle.
The present invention is directed to overcoming one or more of the problems set forth above.